The Pressurized Fluidized Bed Combustion (PFBC) combined cycle has become a subject of world attention in terms of better plant operation, improved plant efficiency, lower flue gas emission and fuel flexibility.
The 71MWe PFBC combined cycle power plant at Wakamatsu, Electric Power Development Company (EPDC) (funded by Ministry of International Trade and Industry (MITI) and Center of Coal Utilization Japan (CCUJ)) achieved approximately 11, 500h accumulative operation while extremely low dust emission (<0.2mg/m3N) was succeeded by a hot gas cleaning system combining cyclones and full scale Ceramic Tube Filter (CTF). The gas turbine installed at the downstream of the CTF was thus completely protected from the possible severe erosion problem with fly ash. Two different configurations of cyclones and CTF were examined in Phases 1 (Conventional PFBC) and Phase2 (Ash Re-circulating PFBC) where several coals, petroleum coke, and two kinds of domestic limestone as absorbent were tested successfully.
CTF is one of key technology for hot gas cleaning. Its major items to be concerned such as the reliability of filter element and dust seal mechanism, the pressure drop performance, the optimization for reverse cleaning conditions and system maintenance-ability are summarized in this paper. Since it's most concerned how long the filter tubes made from Cordierite material can really survive in the commercial use, its life time is confirmed at least several years, based on the physical/chemical analysis of the used filter (approximately 8, 000h) and the accelerated corrosion test with potassium and/or sulfur dioxide gas flow. Increased resistance of gas passage at the seal portion improved the seal between ceramic filter element and metallic parts, avoiding dust leakage. The on-site inspection tool for the filter elements to find any damage suffered and the watching system of plant stability during operation were developed to avoid the catastrophic filter breakage. In conclusion, CTF was confirmed to be applicable for the commercial use.
The future perspective and the application of CTF system are discussed to respond the strong demands for the better environment and the higher efficiency plant using coal.
